The use of "packing" in pumps and other apparatus having reciprocating, slidable or rotatable members for moving fluids or mixed fluids and semi-solids is well known. Packings are typically made up of a resilient or at least compressible material which serves a sealing purpose through its compression and retention of a lubricant, most often an oil or graphite. Rough adjustment of the degree of compression is possible and often necessary on a periodic basis, the adjustment being made typically through the tightening of the member (referred to as a packing gland in a plunger pump) which holds the packing in compression. (Reoiling is sometimes necessary on a periodic basis, the oiling usually applied manually).
Generally, it has been accepted that the packing wears during the operation of pumps and other apparatus utilizing packing in such fluid pumping systems. Thus, leakage occurs around the packing which causes a loss in volumetric capacity of the systems. Moreover, the fluids, often containing undesirable and potentially hazardous components, spill into the vicinity of the pump and overall fluid-moving apparatus. In a plunger pump, the packing gland is made of cast metal and is held to the cast iron plunger housing by bolts. In order to hold and compress the packing in the stuffing box, the gland is tightened down by the bolts to further compress the packing in the stuffing box. Eventually, the packing is no longer effective and must be replaced. To prolong the life of the packing, and avoid the time-consuming replacement of it, a lubricant is often freely applied.
The assembly of the packing gland typically leaves wide tolerances, particularly since the packing gland is cast and the housing and plunger are cast. Therefore, as the plunger moves up and down in a plunger pump, or the pumping element moves otherwise in other pumps, there is often a continuous horizontal shifting of the plunger. This leads to increased wear, sometimes creating an "hour-glass" shape instead of a cylindrical shape, and increased leakage.
Another area of the plunger pump or like pump which requires maintenance and care is the bearing for the eccentric, which is the expedient that allows for pump stroke and capacity variations. In a plunger pump, the eccentric is housed above the plunger and carries the plunger, via a connecting rod, through a particular pump stroke. The bearing used between the eccentric and the connecting rod has been for many years a Babbit bearing which contains lead. The bearings are recognized as a wear item, and are oiled by associated and messy mechanical oilers. Eventually, the liner must be replaced, and this must be done at the expense of operation time. Also, lead poses a disposal hazard, as does the oil from the mechanical oiler which must be used to care for the lead bearing. The use of oil also risks possible contamination of the fluid that is being pumped, and can thus cause an environmental hazard.
In general, the industry has accepted the leakage and maintenance problems associated with plunger pumps and the like pumps. Great effort has not been made to alleviate the shortcomings which have simply been tolerated over the years. The silence of advances in this area must be broken.